Technical Yearbook 2023

FIGURE 1. Pathway of thiol precursors uptake into the wine yeast cell and transformation into volatile thiols.

FIGURE 2. Thiol concentrations in final wines fermented with RUBY™ or a control yeast in Merlot with added thiol precursors (226 g/L sugar, 13.5% v/v potential alcohol, 138 mg/L YAN, 24°C).

thiol management. However, the wine yeast strain plays a key role, as shown in figure 1. Through their cleaving enzymes, wine yeasts can release the aromatic volatile thiols from their non-aromatic conjugated precursors. IRC7 is the gene involved in the formation of the enzyme. Different forms of IRC7 and several combinations of IRC7 alleles exist naturally in yeast. Most of those combinations lead to reduced activity

due to truncated and/or mutated forms of the gene. A comprehensive screening of our collection of wine yeasts highlighted this diversity. Using an innovative non-GMO strategy of cellular division followed by an allelic study, we selected a new wine yeast with fully active IRC7 alleles. This new yeast strain RUBY™ combines excellent characteristics essential in red winemaking and in red wine conditions with the full capacity to reveal volatile thiols.

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TECHNICAL YEARBOOK 2023